Help with algebra hw please?

First you have 450 spots total. Then you know you have 11 big cars and 4 compact. Take the total # of spots and divide it by the number of slots for big and small cars. (450/(11+4) You get 30 meaning that there's 30 sets of spots. So multiply 30 times the number of slots for big cars (30*11=330). Thats the # of large slots. Then do # of small slots times 30. (30*4=120) That's the number of small slots